Metal melting and holding furnace

ABSTRACT

A metal melting and holding furnace having an immersion-type heating unit extending into the furnace body and arranged to provide limited access between the receiving and ladling zones.

Unified States Patent McKenna et al. Aug. 29, 1972 [54] METAL MELTING AND HOLDING FURNACE [56] References Cited [72] Inventors: John Patrick McKenna, Watertown, UNITED STATES PATENTS Wis.; Richard J. Keeling, Lombard, 11 Duane Lauersdorf wateb 2,939,899 6/1960 Edstrand et a1 ..13/29 X town, Wis. 3,293,412 12/ 1966 Profitt et a1 ..219/421 [73] Assignee: Sala Besic Industries, Inc., Milwauprimary Examiner Roy Ema", Jr.

Attorney-Smythe & Moore [22] Filed: Nov. 3, 1970 [57] ABSTRACT [21] Appl. No.: 86,407

A metal melting and holding furnace having an immersion-type heating unit extending into the furnace [52] US. Cl ..13/20, 13/25 body and arranged to provide i d access between [51] Int. Cl ..H05b 3/44, F27d 11/02 the receiving and ladling Zones [58] Field of Search ..13/20, 25, 29; 219/420, 421,

219/422, 426 8 Claims, 5 Drawing Figures METAL MELTING AND HOLDING FURNACE This invention relates to melting furnaces suitable for receiving and melting metal.

Present devices employ a furnace containing a vessel heated on the exterior by electric heating elements, gas burners or oil burners. The vessel transfers heat to the metal contained within it. The use of electric heating elements for such a furnace has the disadvantages of slow heating, limited volume, and expensive components. Also, the use of gas or oil burners in such an arrangement has the disadvantage of having poor temperature control.

Another example of the prior art is a reverberatory type furnace wherein a batch of metal is heated either by radiation from electric elements above the metal therein or gas or oil burners above the metal. In the case of electric elements, required cleaning often results in breakage of the elements, and the furnace is high in cost. When using gas or oil burners, the metal can absorb undesirable byproducts of combustion and the furnace walls usually require daily cleaning.

Still another example of prior art devices is an immersed metal tube in the metal arranged so that gas is burned within the tube to transfer heat to the metal. This is generally limited for use with zinc and zinc alloys.

Other known methods include channel induction furnaces and coreless induction furnaces. The channel induction type is frequently expensive and has some limitations. When used with aluminum, the channels must be frequently cleaned of impurities to prevent failure of the furnace. The coreless induction furnace is not practical for many application, such as when employed at a casting station for hand ladling.

One of the objects of the present invention is to provide a molten metal furnace or vessel which is freeof the disadvantages of the mentioned prior furnaces.

A still further object is to provide a furnace with reduced maintenance which will not require frequent cleaning of walls or channels and does not have a crucible or pot to replace.

Another object is to provide a furnace with an efficiency as near as possible to the induction type.

An additional object is to provide an improved maintenance of specific metal temperature to within .a few degrees of desired point.

In one aspect of the invention, a metal container body is provided which in one form can have sloping side or end walls or both. An immersion-type electric heating unit or assembly extends across the body which is arranged to provide only a limited area of access between a receiving zone on one side of the unit and a ladling zone on the other side. The heating unit can have wells, apertures or chambers therein for receiving one or more heating elements such as silicon carbide elements. In a further form, a chamber can be provided for the ladling zone which can have air or gaseous pressure applied thereto so as to feed or deliver molten metal therefrom.

These and other objects, advantages and features of the invention will become apparent from the following description and drawings which are merely exemplary. In the drawings:

FIG. 1 is a plan view of the furnace; FIG. 2 is a vertical section along the line 2-2 of FIG.

FIG. 3is a vertical section taken along the line 3--3 of FIG. 1;

FIG. 4 is a fragmentary vertical section showing another form of the invention; and

FIG. 5 is a sectional plan view of a modified form of the holder.

Where appropriate, the same reference numerals will indicate similar parts in the various drawings.

The furnace as shown includes a casing or housing 14 which may be of metal and which is lined with heat insulating material 15. The insulating material supports a furnace body 16 which may be built of ceramic or like material. The body is formed with a charging end or zone 17, a heating zone 18, and a ladling end or zone 19.

The charging zone 17 can have sloping outer wall 20 extending at an acute angle to vertical. At its bottom, wall 20 joins the bottom wall 24. Sloping wall 20 permits cleaning of sludge from the furnace and adding of metal ingots.

In adding metal ingots, the cold metal pieces can be slid down wall 20 so as to enter a molten metal bath 31 smoothly without splashing. Further, the slope of wall 20 tends to reduce the volume of metal in the bottom of the furnace where a large volume of metal is unnecessary for normal purposes.

If desired, ladling end 19 can be formed with a sloping outer wall 21 extending at an acute angle to the vertical. At the bottom wall 21 joins the bottom wall 24 of heating zone 18. Sloping wall 21 is advantageous for cleaning of sludge from the furnace and reducing metal volume in the bottom of the furnace. As will be described hereafter, wall 21 may be vertical for auto matic ladling equipment or to accommodate either manual or automatic removal of molten metal.

At the heating zone or center 18, sloping side walls 22 can be used which extend at an acute angle to the vertical. At the bottoms thereof, walls 22 join the bottom wall 24 adjacent heating zone 18. Similar to the other sloping walls, sloping walls 22 are advantageous in reducing metal volume in the bottom of the furnace.

Heating center or zone 18 is arranged to receive electric heating element holder 23 which may have an outside wall 23A of metal or ceramic material. The holders may be rectangular, square, round or other suitable shape and can rest on the bottom 24 of the metal containing body or can be suspended in a suspension frame 238 supported on the top 25 of furnace casing 14. The holder 23 is sized relative to the side walls to permit a minimum access for metal passing between the holder 23 and the sidewalls 22. Such a minimum access area or passage is especially desirable when cold metal is fed into the charging zone 17 A minimum access area as described will prevent any large variation of temperature of the metal in the ladling zone 19 as metal is removed therefrom. The holder 23 conducts heat from the heating elements 26 to the metal bath and protects the heating elements 26 from direct contact with the metal bath. The holder 23 may be arranged to accommodate one or more heating elements 26.

Heating elements 26 may be of commercially availa- I ble electric resistive ceramic material, such as silicon carbide. The elements are obtainable commercially with sleeves 27 and terminal block connections 28.

Insulator 238 may be of ceramic material with high insulating value. The shape of insulator 23B will reduce radiated or conducted heat from holder 23, elements 26 and top surface 30 of the metal bath 31. Such a heat reduction reduces possibilities of electrical connection failures. The insulator 23B also acts as a retainer and support for elements 26.

Terminal guard 31A may be of meshed metal to prevent accidental contact with electrical and relatively hot surfaces.

Special insulated metal shapes 32 can be used as covers to reduce radiated heat loss from metal surface 30 of metal bath 31 and holders 23. Shapes 32 can be made of individual removable sections so that a section can be removed without disturbing the remaining sections.

In the form shown in FIG. 4, the ladling zone or chamber can have an enclosure or crucible 35 including wall 36 having an aperture 37 therein through which metal can flow from the metal bath 31 through the elongated inlet passage 37. Pipe or connection 38 can be alternately connected to vacuum or pressure. Metal discharge pipe 39 will conduct molten metal from the ladling zone to the delivery point 40.

Suitable level control probe means 41 can be used as needed. One example is found in US. Pat. Nos. 2,816,334 and 3,050,794.

In operation, as vacuum is applied to connection 38, molten metal will be drawn through inlet passage 37 into the chamber 42. Then, when gaseous pressure is applied through connection 38, molten metal will be delivered through conduit 39 to delivery point 40.

A ground device 43 (FIG. 2) can be used if desired. Extra recess 44 (FIG. 2) can be formed in the bottom wall to receive a second unit if needed.

An alternate fonn of the holder 23 is shown in FIG. wherein the walls are corrugated for the purpose of thermal stress relief in a refractory block. Also, heating surface area is increased.

It should be apparent that variations can be made in details of construction without departing from the spirit of the invention except as defined in the appended claims.

What is claimed is:

1. In an electrically heated metal melting and holding furnace, the combination including a metal container body having a bottom wall, side walls and end walls, at least one electric heating unit holder extending across and downwardly into said body between said side walls and separating said body into a metal receiving zone and a metal ladling zone, said heating unit means providing limited access for passage of metal between said zones, and electric heating element means extending downwardly in said unit for providing heat to a metal bath in said container body.

2. A furnace as claimed in claim 1 wherein the end walls slope outwardly at an acute angle relative to the bottom wall so as to assist in receiving metal to be melted in the receiving zone and in removing metal from the ladling zone.

3. A furnace as claimed in claim 2 wherein the side walls slope outwardly relative to the bottom wall so as to provide greater available space adjacent the top of the bod as compared to the bottom of the 4. A umace as claimed in claim 1 wherein e heating unit holder means has chambers for receiving electric heating elements.

5. A furnace as claimed in claim 1 wherein the heating unit holder means is removably supported on cross bar means extending across the container body.

6. A furnace as claimed in claim 1 wherein the ladling zone has chamber means extending therein providing a chamber with a metal outlet conduit, and means to apply vacuum and pressure to said chamber means for causing molten metal to be delivered into said chamber means and from said outlet conduit.

7. A furnace as claimed in claim 6 wherein at least one of the end walls slopes outwardly relative to the bottom wall.

8. A furnace as claimed in claim 1 wherein a grounding device is included.

UNITED STATES PATENT OFEICE CERTIFICATE OF CORRECTION Patent No. 3,688,007 Dated August 1972 Inven H John Patrick McKenha et a1 It is certified that error appears in the above-identified patent and that said Letters Patentare hereby corrected as shown below:

Patent Front Page, [73], "Sale." should be Sola Column 2, line 30, comma omitted after "bottom".

Signed and sealed this 13th day of February 1973.

(SEAL) Attest:

ROBERT GOTTSCH ALK EDWARD M.FLETCHER,JR.

Commissioner of Patents Attesting Officer USCOMM-DC 60376-P6D w u.s. sovznuuzu'r rmm'mc omc: nu o-sse-sal,

FORM PO-105O (10-69) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,688,007 Dated August 29, 1972 Inventofl John Patrick McKenna et a1 It is certified that error appears in the above-identified patent and that said Letters Patentare hereby corrected as shown below:

Patent Front Page, [73], "Sale." should be Sola Column 2, line 30, come. omitted after "bottom".

Signed and sealed this 13th day of February 1973 (SEAL) Attest:

EDWARD M .FLETCHER,JR ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PC4050 uscoMM-Dc scan-P69 .5. GOVERNMENT FIUNTING OFFICE 1 I," S68-33r 

1. In an electrically heated metal melting and holding furnace, the combination including a metal container body having a bottom wall, side walls and end walls, at least one electric heating unit holder extending across and downwardly into said body between said side walls and separating said body into a metal receiving zone and a metal ladling zone, said heating unit means providing limited access for passage of metal between said zones, and electric heating element means extending downwardly in said unit for providing heat to a metal bath in said container body.
 2. A furnace as claimed in claim 1 wherein the end walls slope outwardly at an acute angle relative to the bottom wall so as to assist in receiving metal to be melted in the receiving zone and in removing metal from the ladling zone.
 3. A furnace as claimed in claim 2 wherein the side walls slope outwardly relative to the bottom wall so as to provide greater available space adjacent the top of the body as compared to the bottom of the body.
 4. A furnace as claimed in claim 1 wherein the heating unit holder means has chambers for receiving electric heating elements.
 5. A furnace as claimed in claim 1 wherein the heating unit holder means is removably supported on cross bar means extending across the container body.
 6. A furnace as claimed in claim 1 wherein the ladling zone has chamber means extending therein providing a chamber with a metal outlet conduit, and means to apply vacuum and pressure to said chamber means for causing molten metal to be delivered into said chamber means and from said outlet conduit.
 7. A furnace as claimed in claim 6 wherein at least one of the end walls slopes outwardly relative to the bottom wall.
 8. A furnace as claimed in claim 1 wherein a grounding device is included. 